【作者】 张彦军；

【导师】 常海萍；

【作者基本信息】 南京航空航天大学 ， 航空宇航推进理论与工程， 2009， 硕士

【摘要】 气溶胶红外隐身技术是针对飞机发动机喷口的热部件及发动机排出的高温燃气在3~5μm及8~14μm波段的红外辐射而研究的一种有效的隐身方法,在相同的材料特性条件下,气溶胶粒子的分布特征成为影响气溶胶红外辐射抑制效果的主要因素。本文基于气固两相流理论,借助商业CFD计算软件FLUENT,对含离散颗粒的热喷流进行数值计算。首先对含离散颗粒热喷流计算模型进行研究,分析不同计算模型对计算结果的影响,其中,湍流模型对气相的速度场的计算结果影响较大,而对温度场和组分浓度场的计算结果影响不大。经比较发现Realizable k-ε湍流模型更适合于本文的研究对象。在计算中,计算域长度需要取到L/D≈26。然后运用实验的方法对所选计算模型的合理性进行验证。设计了一套含离散颗粒喷流试验系统,包括供气系统、下粉装置、喷嘴及PIV测量系统。实验中采用PIV测量技术对含离散颗粒喷流的速度场和颗粒浓度场进行测量,结果与数值模拟结果基本一致。在实验验证了计算模型的合理性的基础上,着重分析了不同离散颗粒喷射量、喷射角度、喷射速度及外围气流速度对离散颗粒在流场中的分布特征的影响规律:当外界气流M =0时,增加颗粒喷射量能有效提高气溶胶颗粒在空间各点的浓度,但对颗粒在空间的分布影响较小;增加颗粒喷射速度对离散颗粒浓度分布影响较小;喷射角度为0度时空间各点浓度分布比较均匀;随外界气流速度提高,颗粒与气流开始发生掺混的位置逐渐后移,外界气流速度越大,颗粒浓度场的扩散角越小,且空间各点颗粒浓度越小。更多还原

【Abstract】 Aerosol obscure is an effectual technique of I.R. suppression, which is applied to decrease the I.R. radiation of heat exhaust and hot nozzle in the bands from 3μm to 5μm and 8μm to14μm. In the same material condition, the distribution characteristics of discrete should be the main factor that affects the suppression effect.Based on the gas-solid two-phase flow theory, numerical simulation of heat exhaust with particles is done by using the commercial CFD software FLUENT. First of all, we do research on the calculation model of heat exhaust with particulates, try to find the influence of different models on the calculation results. It is Realized that the turbulence models have great influence on the velocity field and little influence on the temperature field and concentration field. By comparison, Realizable k-εmodel is the best suitable one for this calculation model. The calculation domain needs to be L / D≈26 in length. And then an experiment is done to verify the reasonableness of our calculation model. This experimental system mainly includes gas supply system, particle dropping system, aerosol injection system and PIV measurement system. We get the velocity field and the concentration field in the experiment. Within limits, the numerical calculation results closely fit the experimental results. After the reasonableness of the calculation model is proved, the analysis focuses on the influence law of injection amount, velocity, angle and the velocity of external stream on the distribution of discrete particles. When the velocity of external stream is 0, to increase the particle injection amount can effectively increase the particle concentration in space, but the distribution of particles in space is less influenced and so do the increase of injection velocity. When the injection angle is 0 degree, the concentration of the particles is evenly distributed. With increase of the external stream velocity, the position that the particles and hot exhaust begin to mix together is getting further. The higher the velocity of the external stream is, the smaller the diffusion angle of the particle concentration field and the particle concentration value is.更多还原